Hair colouring can be divided into two main types, permanent and semi-permanent. Permanent hair colouring is achieved through the use of oxidation dyes. The process is typically performed under basic conditions. Ammonia opens the hair shaft pores so that the dye can bond with the hair. Semi-permanent hair dye only penetrates the hair shaft and therefore will be washed out after repeated washing.
Because of their high compatibility with a variety of hair dyes, low viscosity Celopre® H grades can stabilise the suspension of dyes in the formulation and adjust the application viscosity of the hair colours.